Low wear tilting mechanism

ABSTRACT

A sorting conveyor for transporting objects and unloading objects at one or more unloading stations adjacent the conveyor. Each of the tilting conveyor carts includes a trailer frame base, a carrying tray for holding the objects and a tiltable support apparatus for supporting the carrying tray above the trailer frame base and for allowing tilting of the carrying tray towards at least one side of the conveyor to unload objects into unloading stations on at least one side of the conveyor.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates generally to package sorting conveyors andmore particularly relates to an improved tilting mechanism for a tiltingconveyor cart.

(2) Description of the Related Art

Conveyor systems having a number of individual carrying carts have beencommonly used for many years to carry and sort packages or other items,such as mail. For example, U.S. Pat. No. 5,054,601 to Sjogren et al.discloses a package sorting conveyor comprised of a train of tilt traycarriers coupled in tandem to form a continuous loop. Each carrierincludes a pivotally mounted tilt tray normally maintained in an uprightposition. The carriers are moved around the loop by a series of motorsspaced around the loop. Branching out from the loop are outfeed chutesor the like for receiving packages from the carriers. When a particularcarrier holding a particular package to be sorted reaches a selectedoutfeed chute, an actuator tilts the tray to dump the package into theoutfeed chute. Another example of a typical package sorting conveyor isdisclosed in International PCT Application Number PCT/DK90/00047 ofKosan Crisplant A/S.

One significant disadvantage of conventionally designed package sortingconveyors is that conventional conveyor carriers laterally tilt only ona horizontal axis parallel to the direction of conveyor travel. Whilethis accomplishes the objective of dumping the package from the carrierinto an outfeed chute or the like, the package is often roughly tumbledor rolled, sometimes damaging the package's contents. One reason forthis is that the packages typically are unloaded from the carrier whilestill traveling forward at the same speed as the conveyor. Thus,packages tend to slam into a forward retaining wall of the outfeed chutebefore sliding down the chute. Another problem with conventionallaterally tilting conveyors is that because the packages are movingforward at full speed when they are unloaded into the outfeed chute, theoutfeed chute must be relatively wide so that packages do not miss thechute and fall off the conveyor past the chute. This often unnecessarilyincreases the overall size of the conveyor system.

U.S. Pat. No. 4,744,454 and an improvement thereto, U.S. Pat. No.5,086,905, both to Polling, disclose previous attempts to remedy thisproblem of rough handling by conventional laterally tilting conveyorcarriers. Both of these patents to Polling disclose a conveyor elementfor a package conveyor that includes a tilting carrier tray mounted tobe rotatable about two swivel axes. A first swivel shaft extendsobliquely downward from the underside of the carrying tray and is inturn connected at an angle to the end of a second swivel shaft extendingobliquely upwards from a base support part of the conveyor element.Together, the two swivel shafts form a "V" that points in the directionof conveyor travel. Both of the swivel shafts lie in the vertical planeof symmetry of the conveyor element when the carrier tray is disposed inits upright position.

Because the carrier tray of Polling rotates about two oblique axes, thecarrier tray can be tilted not only lateral on a horizontal axis, but ismoved through a geometrically complex spatial reorientation duringpackage discharge. This allows for more gentle placement of a package onan outfeed chute than can be accomplished using conventional conveyortrays that laterally tip on only a horizontal axis. The Polling conveyorelement more gently handles the packages by imparting some degree ofrearward velocity to the packages as they are discharged, which, whenadded to the forward velocity of the conveyor system, results in thepackages' forward velocity during discharge being less than that of theconveyor system itself.

However, the conveyor elements of both of Polling's patents are undulycomplicated and intolerant of manufacturing discrepancies. In fact, thesecond Polling conveyor element (U.S. Pat. No. 5,086,905) was inventedin an attempt to simplify the original design disclosed in the firstPolling patent (U.S. Pat. No. 4,744,454), which had proved to be tooexpensive and complicated to manufacture efficiently. As a result ofthis complexity and cost, the Polling devices have not enjoyedsignificant commercial acceptance and success.

One solution to these problems is shown in U.S. application Ser. No.08/632,012, filed Apr. 15, 1996, which is hereby incorporated byreference in its entirety. One feature of this reference is the use of apull-down design for tilting the improve trays.

Another example of a sorter conveyor using a pull-down design fortilting its trays is shown in U.S. Pat. No. 5,664,660, issued to Prydtz.The '660 patent is directed to a sorter conveyor having laterallytiltable transport trays, instead of a conventional transport chaindriven by a driving station, in which a driving wheel or worm cooperateswith the chain links, these being advanced arranged with guiding railsalong a small mutual spacing and carrying both the transport trays andthe tilt mechanisms associated therewith, which conventional arrangementcauses considerable problems with respect to tolerances for both thelongitudinal pitch of the chain links and the mounting of the guidingrails. The invention includes carts that are advanced along mutuallywidely spaced guiding rails, whereby the tolerance demands on the latterare reduced considerably. Also, the carts are advanced by way ofstationary linear motors, which, supposedly, renders any tolerancedemands on the longitudinal pitch of the tray units entirelysuperfluous. Also the tilting mechanisms may be given a very simpledesign according to the patent. However, it has been discovered thatthere are operational problems associated with this type of design,especially the operation of its linear motors and tilting mechanism.

While the design shown in U.S. application Ser. No. 08/632,012, filedApr. 15, 1996 overcomes some of the problems associated with the priorart designs, some problems have begun to surface over time as the unitshave been operated. Specifically, there was a problem of wear on thepivot switch used to capture the wheel of the pull-down mechanism.

When the pivot switch is projected in front of the wheel, the wheelstrikes the wall of the pivot switch and the wheel is rotating when thestrike is made. The axle of the wheel is perpendicular to the directionof travel while the wall of the pivot switch is 30 degrees off ofdirection of travel. With the wheel rotating "lathe" action takes placebetween the pivot switch, wall and the wheel.

After the initial strike between the wheel and the pivot switch, thepressure between the two is relieved until the wheel has traveled pastthe pivot point and then the "lathe" action again repeats itself withthe wear occurring on the pivot switch's tail.

Initially, a styrene wheel was used with a nylon pivot switch. The pivotswitch was protected, but the wheel became sacrificial. Because therewould be many more wheels to replace than pivot switches, it waspreferable to fabricate the wheel from nylon and the pivot switch fromDelrin® plastic, so that the wear appears on the pivot switch ratherthan the wheel. However, eventually the wheel wears the pivot switchsufficiently that the wheel can jump out of the track of the pivotswitch and cause a missed tip which can also cause "cascading errors".

"Cascading errors" were first discovered when audits at the end of thechute indicated there were more errors occurring than were predicted bytray verification. Normally, when a tray is to tip to the right,immediately before the tray is being straightened, a series ofphotocells determines if the right hand arm is in the "low" or "tipped"position or the "up" or "latched" position. If the controls said thatthe arm should be tipped and the verifier says that the arm is tippedthen it was assumed that the product went down the correct chute.However, in certain cases, tray verification would predict five errorsbut chute audits would indicate 35 errors. This previously unknowneffect is referred to in this application as "cascade errors".

Most pull-down tilting mechanisms are actuated by spring when the pivotswitch is released by an energizing solenoid. In other words, the pivotswitch is spring-biased in the "out" position but held in the retainedposition by the solenoid.

When the computer provides a pulse, the solenoid plunger retracts,enabling the pivot switch to spring into the "out" position. The wheelstrikes the pivot switch in front of the pivot point and the pivotswitch unlatches the carriage and then as the wheel strikes the tail ofthe pivot switch, it pushes the pivot switch back to the home positionand the spring on the solenoid plunger pushes the plunger into a detentcapturing the pivot switch in the home position. The computer initiatesthe unlatch but it is the action of the wheel on the tail that normallyrelatches it.

If the solenoid does not return to capture the pivot switch before thewheel leaves the pivot switch's tail or a wheel is missing or broken,this will allow the pivot switch to move away from its intended homeposition back into the engagement position. The next tilt module that isnot in the down position will then strike the pivot switch, tilt, andreset the pivot switch. If the pivot switch relatches properly thistime, then that particular pivot switch will cause no more errors. Ifthe pivot switch does not relatch it can again go into the engagedposition and cause additional problems.

The cascade effect, though, comes from the first carriage that wastipped incorrectly, for if it were assigned a tilt position furtherdownstream, when that carriage (which has been tilted incorrectly) getsin position to unload, the pivot switch at the proper destination chutewill move into the engagement position. But because that arm has beenincorrectly tipped upstream, no action will take place and the pivotswitch will stay in the out position until the next untipped carriagearrives. That carriage will then be tipped at the wrong destination andshould cause that pivot switch to relatch. If that particular tray wasassigned a chute destination further downstream, when it arrives at itsproper destination, the pivot switch will move into the engagementposition, but again cannot engage because the tilt module is already inthe low position, the tilt module will pass by and will not relatch thepivot switch. This pivot switch will then stay in the out positioncapturing the wheel of the next tilt module that is not tipped. Thiserror will than continue to cascade downstream until eventually theerror will pass the last destination and the system should heal itself.

However, there are some conditions that can exist that cause the errorto not heal itself but continue to cause problems. An example would beif a particular tilt module were missing a wheel; that tilt module couldthen be loaded and when it gets to its destination, the pivot switchwill go out to engage the wheel but with no wheel the module will nottip. The pivot switch will then catch the next available tray beginningthe cascade problem. This will continue to repeat itself and will occurand start cascade error any time the tray with the missing wheel isassigned a destination.

One attempted solution to this problem is to use the tip verificationswitch to shut the sorter down if the pivot switch does not return tothe "home" position within a given time period. However, with a largesorter this requires a maintenance man to then check the pivot switch tosee if it should be reset and whether a wheel is missing. In themeantime, everything just sits on the sorter. For time criticalapplications, such as airline baggage sorting, this delay may beunacceptable.

Thus, there remains a need for a new and improved tilting mechanism fortilting a conveyor tray that reduces the chance of a mis-tip while, atthe same time, is an uncomplicated design that is inexpensive and simpleto manufacture and service.

SUMMARY OF THE INVENTION

The present invention is directed to an improved tilting mechanism for aconveyor cart for a sorting conveyor for transporting objects andunloading objects at one or more unloading stations adjacent theconveyor. Generally, the sorting conveyor includes: a conveyor track; atrain of the tilting conveyor carts connected end-to-end; and a powersource for moving the conveyor carts on the conveyor track. In thepreferred embodiment, the power source is a linear induction motor.

Each of the tilting conveyor carts includes a trailer frame base. Thetrailer frame includes a roller structure for engaging the conveyortrack, a driven member responsive to the power source, and a hitchmechanism for connecting each tilting conveyor cart to an adjacentconveyor cart. The conveyor cart also includes a carrying tray forholding the objects and a tiltable support apparatus for supporting thecarrying tray above the trailer frame base and for allowing tilting ofthe carrying tray towards at least one side of the conveyor to unloadobjects into unloading stations on at least one side of the conveyor.

The tilting mechanism tilts the carrying tray on the tiltable supportapparatus to thereby unload objects into one of the unloading stationsadjacent the conveyor. The improved tilting mechanism includes a pair ofactuating arms attached to the carrying tray on opposite sides of thetiltable support apparatus and a pull-down mechanism associated witheach unloading station for selectively pulling down one of the actuatingarms so as to pull one side of the carrying tray downwardly andrearwardly into a tilted position.

In the present invention each of the actuator arms includes a rollerwheel on a lower end of the actuator arm and a bumper assembly locatedin front of the leading inside edge of the roller wheel to reduce wearbetween the wheel and the tipping mechanism. In the preferredembodiment, the bumper assembly includes a downwardly extending,vertically oriented bumper and a bracket for positioning the downwardlyextending, vertically oriented bumper with respect to the inside leadingedge of the roller wheel.

Accordingly, one aspect of the present invention is to provide a sortingconveyor for transporting objects and unloading objects at one or moreunloading stations adjacent the conveyor. The sorting conveyorincluding: (a) a conveyor track; (b) a train of tilting conveyor cartsconnected end-to-end; (c) a power source for moving the conveyor cartson the conveyor track; (d) each of the tilting conveyor cartscomprising: (i) a trailer frame base, including: a roller structure forengaging the conveyor track, a driven member responsive to the powersource, and a hitch mechanism for connecting each tilting conveyor cartto an adjacent conveyor cart; (ii) a carrying tray for holding theobjects; and (iii) a tiltable support apparatus for supporting thecarrying tray above the trailer frame base and for allowing tilting ofthe carrying tray towards at least one side of the conveyor to unloadobjects into unloading stations on at least one side of the conveyor,the tiltable support apparatus including: (i) an upper support structurejoined to the carrying tray, (ii) a lower support structure joined tothe trailer frame base, and (iii) a pivot structure connecting the uppersupport structure to the lower support structure along a pivot axis; and(e) a tilting mechanism for tilting the carrying tray on the tiltablesupport apparatus to thereby unload objects into one of the unloadingstations adjacent the conveyor, wherein the tilting mechanism includes:(i) a pair of actuating arms attached to the carrying tray on oppositesides of the tiltable support apparatus; and (ii) a pull-down mechanismassociated with each unloading station for selectively pulling down oneof the actuating arms so as to pull one side of the carrying traydownwardly and rearwardly into a tilted position; wherein each of theactuator arms includes a roller wheel on a lower end of the actuator armand a bumper located in front of the leading inside edge of the rollerwheel, and wherein the pull-down mechanism includes a descending rampadjacent the conveyor track and a laterally pivoting switch for engagingthe bumper and directing the roller wheel of a selected actuator arminto the descending ramp.

Another aspect of the present invention is to provide a bumper assemblyfor a tilting cart for a sorting conveyor, the tilting cart including acarrying tray, a tiltable support apparatus and a tilting mechanism fortilting the tiltable support apparatus on the tilting cart to therebyunload objects into one of the unloading stations adjacent the conveyor,wherein the tilting mechanism includes: (i) a pair of actuating armsattached to the carrying tray on opposite sides of the tiltable supportapparatus; and (ii) a pull-down mechanism associated with each unloadingstation for selectively pulling down one of the actuating arms so as topull one side of the carrying tray downwardly and rearwardly into atilted position, wherein each of the actuator arms includes a rollerwheel on a lower end of the actuator arm and wherein the pull-downmechanism includes a descending ramp adjacent the conveyor track and alaterally pivoting switch for engaging the bumper and directing theroller wheel of a selected actuator arm into the descending ramp. Thebumper assembly includes: (a) a downwardly extending, verticallyoriented bumper; and (b) means for positioning the downwardly extending,vertically oriented bumper with respect to the inside leading edge ofthe roller wheel.

Still another aspect of the present invention is to provide a sortingconveyor for transporting objects and unloading objects at one or moreunloading stations adjacent the conveyor. The sorting conveyor includes:(a) a conveyor track; (b) a train of tilting conveyor carts connectedend-to-end; (c) a power source for moving the conveyor carts on theconveyor track, wherein the power source comprises a linear inductionmotor; (d) each of the tilting conveyor carts comprising: (i) a trailerframe base, including: a roller structure for engaging the conveyortrack, a driven member responsive to the power source, and a hitchmechanism for connecting each tilting conveyor cart to an adjacentconveyor cart; (ii) a carrying tray for holding the objects; and (iii) atiltable support apparatus for supporting the carrying tray above thetrailer frame base and for allowing tilting of the carrying tray towardsat least one side of the conveyor to unload objects into unloadingstations on at least one side of the conveyor, the tiltable supportapparatus including: (i) an upper support structure joined to thecarrying tray, (ii) a lower support structure joined to the trailerframe base, and (iii) a pivot structure connecting the upper supportstructure to the lower support structure along a pivot axis; and (e) atilting mechanism for tilting the carrying tray on the tiltable supportapparatus to thereby unload objects into one of the unloading stationsadjacent the conveyor, wherein the tilting mechanism includes: (i) apair of actuating arms attached to the carrying tray on opposite sidesof the tiltable support apparatus; and (ii) a pull-down mechanismassociated with each unloading station for selectively pulling down oneof the actuating arms so as to pull one side of the carrying traydownwardly and rearwardly into a tilted position; wherein each of theactuator arms includes a roller wheel on a lower end of the actuator armand a bumper assembly located in front of the leading inside edge of theroller wheel, the bumper assembly including: (i) a downwardly extending,vertically oriented bumper; and (ii) means for positioning thedownwardly extending, vertically oriented bumper with respect to theinside leading edge of the roller wheel, and wherein the pull-downmechanism includes a descending ramp adjacent the conveyor track and alaterally pivoting switch for engaging the bumper and directing theroller wheel of a selected actuator arm into the descending ramp.

These and other aspects of the present invention will become apparent tothose skilled in the art after a reading of the following description ofthe preferred embodiment when considered with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of a package sorting conveyorconstructed according to the present invention;

FIG. 2 is front, elevational view of a single tilting conveyor cart ofthe package sorting conveyor and the power source of the conveyor;

FIG. 3 depicts a train of trailer frame structures of the conveyorcarts, as seen from the top, but with the tiltable support apparatusesand the carrying trays of the conveyor carts removed for clarity;

FIG. 3A depicts a top view of an axle caster that holds a roller wheelon one of the conveyor carts;

FIG. 3B is a cross-sectional view of the axle caster and roller wheel ofFIG. 3A, taken along lines 3B--3B;

FIG. 4 is an elevational side view of one of the tilting conveyor cartsof the present invention;

FIG. 5 is a sectional side view of a tilting conveyor cart, taken alonglines 5--5 of FIG. 2, which shows the tiltable support apparatus and theangled pivot structure of the tilting conveyor cart of the invention;

FIG. 5A is a geometric depiction of the conveyor cart pivot axis andconveyor line of travel as they relate to three-dimensional X, Y, Zspatial coordinates;

FIG. 6 is a top view of the train of carts of the package sortingconveyor of the present invention;

FIG. 6A shows the train of carts of FIG. 6, but with one of the carts inits tilted position and unloading a package onto an unloading stationbeside the sorting conveyor track;

FIG. 7 is a rear view of the tilting conveyor cart taken along lines7--7 of FIG. 4 with the track rails and the roller structure omitted forclarity, which shows the conveyor cart in its upright, horizontalposition;

FIG. 7A shows the tilting conveyor cart of FIG. 7 in its tiltedposition;

FIG. 8 is a side elevational view of the pull-down mechanism of theinvention with its switch in an open position as it captures a passingroller wheel on a conveyor cart actuating arm;

FIG. 8A is another side view of the pull-down mechanism, except with theroller wheel traveling through the descending ramp and the switch in itsclosed position;

FIG. 9 is a top view of the pull-down mechanism with the switch in itsopen position, capturing a passing roller wheel;

FIG. 9A is another top view of the pull-down mechanism, except with theroller wheel traveling through the descending ramp and the switch in itsclosed position;

FIG. 10 is a top view of the push-up mechanism with the bumper assemblyshown angled for clarity;

FIG. 10A is a side view of the push-up mechanism;

FIG. 11 is a side view of the bumper assembly; and

FIG. 11A is a top view of the bumper assembly with the bumper 154removed from clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, like reference characters designate likeor corresponding parts throughout the several views. Also in thefollowing description, it is to be understood that such terms as"forward", "rearward", "left", "right", "upwardly", "downwardly", andthe like are words of convenience and are not to be construed aslimiting terms.

Referring now to the drawings in general and FIG. 1 in particular, itwill be understood that the illustrations are for the purpose ofdescribing a preferred embodiment of the invention and are not intendedto limit the invention thereto. As seen in FIG. 1, a sorting conveyor,generally designated 10, is shown constructed according to the presentinvention for transporting and sorting packages 11 or other objects. Thesorting conveyor 10 comprises a train of individual carts 20, connectedend to end, which preferably form an endless loop around aclosed-circuit conveyor track 12. Alternately, the conveyor carts 20 ofthe invention could be used singly or as part of a finite train.

The package sorting conveyor 10 generally includes four majorsub-assemblies: a conveyor track 12; a power source 70; the train oftilting conveyor carts 20, which are moved along the conveyor track 12by the power source 70; and a tilting mechanism 80 for tilting theconveyor carts 20 to discharge packages 11 therefrom. Typically, anynumber of unloading stations or outfeed chutes 18, which are adjacentthe package sorting conveyor 10 on one or both sides thereof, receivethe packages 11 discharged from the sorting conveyor 10 and carry thepackages to waiting storage bins, trucks, etc. Packages may be manuallyplaced on the conveyor carts 20 or may be delivered to the sortingconveyor 10 via infeed chutes 17 or the like.

The conveyor track 12 includes two parallel rails 14 and may be built toconform to the layout of any warehouse, shipping center, distributioncenter, or the like. Best seen as resembling the track of a rollercoaster, the conveyor track 12 may be substantially horizontal or mayascend and descend. The conveyor track rails 14 may lie in the samehorizontal plane, or one may be higher than the other, such as would bethe case in a banked curve in the track 12. Banked curves are greatlyadvantageous because they allow the conveyor carts 20 to move around acurved conveyor track 12 at a much greater speed without spillingpackages 11 than on a flat track. Preferably, the rails 14 are generallytubular, again similar to a roller coaster, and are supported by railsupport members 16 only on the outwardly facing edges of the rails. Therails 14 may be round or rectangular in cross-section. Rectangularcross-section is preferred since it has been found that round railscause the roller wheels to wear somewhat in their center because theload is not as well distributed as when rectangular rails are utilized.

The power source 70 of the sorter conveyor 10, which is shown in FIG. 2,is preferably a vertically oriented linear induction motor (LIM). Thevertically oriented LIM 70 of the present invention is an improvementover previously designed LIM's, which typically are horizontallydisposed below the conveyor track. Conventional LIM's also usuallydepend on the presence of a heavy steel plate in each conveyor cart toprovide a pathway through which electromagnetic flux from theelectromagnetic coil of the LIM passes, thereby driving the carts alongthe track. This causes two problems. The first problem is with excessiveweight of the conveyor cart train resulting from the presence of thesteel plates.

The second problem is with maintaining the proper distance between theelectromagnetic coil of the LIM and the conveyor cart, because gravitycoupled with magnetic attraction constantly try to pull the conveyorcart downwardly towards the electromagnetic coil. Magnetic attraction,which attracts the cart towards the electromagnetic coil, accounts forapproximately ten percent of the force generated by the electromagneticcoil. Longitudinal thrust, which drives the conveyor cart train aroundthe conveyor track, accounts for approximately ninety percent of theforce generated by the electromagnetic coil. While the ten percentmagnetic attractive force is relatively weak compared to the ninetypercent longitudinal thrust force, it is still enough to pull theconveyor cart into contact with the electromagnetic coil, especiallywhen assisted by gravity in a configuration where the LIM ishorizontally disposed below the conveyor track. If the conveyor cart isdrawn into contact with the electromagnetic coil, the carts are frozenin place because even the ninety percent longitudinal thrust componentof the LIM's total force cannot overcome the friction created by thecontacting surfaces magnetically held together. This contact andresulting conveyor failure is normally prevented by maintaining adistance between the conveyor cart and the electromagnetic coil withwhatever apparatus is used to support the train of conveyor cartsmoveably on the conveyor track. However, as parts wear, the distancebetween the conveyor carts and the electromagnetic coil is reduced untilcontact and resulting conveyor cart seizure is likely to occur.

The LIM 70 of the present invention solves both of these problems in twodifferent ways. First, the conventional steel flux plate is replacedwith a second electromagnetic coil 72b, which is preferably identicalto, but out-of-phase with, a first electromagnetic coil 72a. Eachelectromagnetic coil thus performs the function of the steel plate forthe other electromagnetic coil, i.e. electromagnetic coil 72a provides aflux path for electromagnetic coil 72b and vice versa. Elimination ofthe conventional steel plate reduces the weight of and, accordingly, theenergy required to move the train of conveyor carts 20.

Second, the LIM 70 is vertically oriented so that a driven fin 36, whichis attached to the bottom of each conveyor cart 20, hangs downwardly inbetween the two electromagnets 72a,b. Composed of aluminum or otherconductive metal, the vertical fin 36 preferably has swept-back front36a and rear 36b edges, as shown in FIG. 4, giving the fin 36 agenerally parallelogram shape to reduce damage in the event the finwould contact a structure and to distribute the air gap over the lengthof the LIM to reduce heat and provide more constant thrust. Verticallyorienting the fin 36 and the LIM 70 greatly reduces problems withmaintaining proper spacing between the fin 36 and the electromagnets72a,b, because gravity ceases to be a factor as the weight of the liveload varies and because the two electromagnets 72a,b, both attract thefin 36 equally. This results in the fin 36 being easily maintainedequidistant between the two electromagnets 72a,b of the LIM 70 of theinvention, thereby preventing the fin 36 from contacting one of theelectromagnets and being seized in place as described above.

The electromagnets 72a,b are out-of-phase with respect to each other sothat the inductive force they create will flow in the same direction. Inother words, the electromagnets 72a,b are electrically out-of-phasewhile physically opposed to each other so as to supplement each other'sinductive forces on the fin 36, instead of canceling each other out.This helps provide a consistent motive force on the train of conveyorcarts because longitudinal thrust remains constant even if the fin 36 ispulled slightly closer to one of the electromagnets 72a,b of the LIM 70.While the longitudinal thrust is thereby increased with respect to thecloser electromagnet, the longitudinal thrust with respect to the moredistant electromagnet is proportionally decreased. Thus, totallongitudinal thrust in the direction or line of travel remains constanteven if the fin 36 wavers slightly from side to side. While a smalldegree of lateral fin movement may occur, the structure of the carts andthe opposing pull of the electromagnets 72a,b prevent any changes in thetotal thrust if the fin is pulled in close proximity with eitherelectromagnet. The LIM 70 ordinarily moves the train of conveyor carts20 in one direction of travel; however, it can also be reversed ifnecessary to run the sorting conveyor backwards by reversing the phases.

Now turning to the train of tilting conveyor carts 20, each cart 20includes three major sub-assemblies, shown best in FIG. 2: a trailerframe structure 22, a generally horizontally disposed carrying tray 40for holding the packages 11, and a tiltable support apparatus 50 forsupporting the carrying tray 40 above the trailer frame structure 22 andfor allowing tilting of the carrying tray 40 towards either side of thesorting conveyor 10 to unload a package into one of the unloadingstations. Each cart 20 is built around a base trailer frame structure 22to which other components of each cart 20 are mounted. As shown in FIG.3, the trailer frame structure 22 includes a longitudinal base member 24that extends in the direction of conveyor travel 64 between the twoparallel rails 14. Preferably, the base member 24 is substantiallyequidistant from each rail 14.

A roller structure 26 for riding on the conveyor track 12 is mounted ona front end of the base member 24 and includes two laterally extendingroller wheel mechanisms 27, one for each rail 14. The reason for theoutboard placement of the rail supports 16 and the tubular shape of therails 14 becomes apparent upon examining the roller wheel mechanisms 27.Each roller wheel mechanism 27 includes three roller wheels: an upperroller wheel 30a for riding on the top edge of the rail 14, a middleroller wheel 30b for riding on an inside edge of the rail 14, and alower roller wheel 30c for riding on the bottom edge of the rail 14.With this configuration, it is almost impossible for a cart 20 to jumpthe track 12, because a wheel is provided for each directional force(sideways, upward, and downward) that a cart 20 may encounter whentraveling along the track 12. Preferably, each roller wheel 30a,b,c isconstructed of a somewhat resilient material such as polyurethane toprovide for smooth, quiet, relatively vibration-free operation of thesorter conveyor 10.

Referring now especially to FIGS. 3A and 3B, the structure of eachroller wheel mechanism 27 that holds the top wheel 30a is shown ingreater detail. Each top roller wheel 30a is retained by an axle caster28 that is preferably formed from extruded aluminum or the like. Theaxle caster 28 includes two forks 28a and 28b, one on each side of thewheel 30a, and a bearing bore 28c disposed at the juncture of the twoforks 28a,b, which has an opening 28d on one side so that the bearingbore 28c communicates with the space between the forks 28a,b. A pair offlange bearings 29 seated in the bearing bore 28c are disposed around anaxle shaft 27a extending from the roller structure 26. Preferably formedof "oilite" or other friction-reducing material, each flange bearing 29has the form of a top-hat bushing and includes a center hole 29a throughwhich passes the axle shaft 27a. The roller wheel 30a is held in placebetween the two forks 28a,b by a bolt 31 and nut 31a. Preferably, theroller wheel 30a includes a bearing structure 30d disposed around thebolt 31, which serves as an axle running through the center of the wheel30a.

The axle caster shown in FIGS. 3A and 3B represents an improvement overexisting axle casters that hold roller wheels. Due to wear, axle castersinevitably tend to become loose and allow the roller wheels to chatterback and forth, which would inhibit smooth, quiet, vibration-freeoperation of a sorting conveyor. However, previously designed axlecasters typically have a bearing around the axle shaft that must bepressed out when worn and replaced with a new bearing that must bepressed in. This requires a press in addition to more time and expensethan is desirable in a large sorting conveyor system.

The axle caster 28 of the present invention solves this problem byproviding that the flange bearings 29 can easily be slid into place byhand into the bearing bore 28c without using a press. Then, to immovablysecure the flange bearings 29 inside the bearing bore 28c, the forks28a,b are slightly flexed inwardly towards each other as the nut 31a istightened onto the bolt 31 to hold the wheel 30a in place. The forks28a,b of the axle caster 28 are therefore formed minutely wider apartthan would be necessary to merely hold the wheel 30a. When the forks28a,b are flexed inwardly towards each other by tightening the nut 31aon the bolt 31, the opening 28d of the bearing bore 28c is closedsomewhat and the bearing bore 28c is itself slightly distorted, securelyretaining the flange bearings 29 therein. The flange bearings 29themselves are, however, not significantly distorted and are free toswivel back and forth on the axle shaft 27a.

Therefore, the flange bearings 29 can easily and immediately be replacedon-site when worn, eliminating much down-time that would be required ifconventionally designed axle casters were used in the conveyor cart 20of the present invention.

Adjacent carts 20 in the train are connected together using hitchmechanisms 32. Each hitch mechanism 32 is shown in FIGS. 3 and 4 asincluding a front hitch 32a mounted on the front end of the base member24 in front of the roller structure 26 and a rear hitch 32b mounted onthe rear end of the base member. In the embodiment disclosed, each hitch32a,b has a vertical throughbore, through which a hitch pin connector32c is inserted. Preferably, the hitch mechanisms 32 are configured sothat the front hitch 32a on a rearward cart is disposed overtop of therear hitch 32b on a forward cart. In the alternative, the hitchmechanisms 32 may comprise a poly-directional spherical ball jointmechanism similar in structure to an automotive trailer hitch. In eithercase, friction between hitch mechanism components is preferably reducedby, for example, lining the hitch components with TEFLON or otherrelatively friction-free material.

To prevent adjacent conveyor carts 20 from separating should the hitchmechanism 32 accidentally break or become uncoupled, an auxiliary cartconnector 34 is preferably connected between the trailer framestructures 22 of adjacent carts 20. In the preferred embodiment, theauxiliary cart connector 34 is a metal cable or lanyard, although otherhigh-tensile strength materials could be used. In the embodimentdepicted, the auxiliary cart connector 34 is an approximately 3/16thinch thick metal cable connected to adjacent trailer frame structures 22with metal mounting connectors 34a.

The primary reason that metal is the preferred material for theauxiliary cart connector 34, besides its strength, is so that theauxiliary cart connector 34 will also serve as a continuous electricalconnector between adjacent carts 20. Electrical continuity between carts20 is important because of static electricity build-up while the carts20 are traveling around the conveyor track 12. However, because theroller wheels 30a,b,c are preferably formed of polyurethane (anelectrical insulator) and because the components of the hitch mechanism32 are preferably coated with TEFLON (also an electrical insulator),electrical continuity between adjacent carts 20 would not otherwise beeffectively achieved. By electrically connecting the carts 20, staticcharges can be bled off from the train, which is important for safetyand operational considerations. Thus, the auxiliary cart connector 34serves two important purposes: first, it physically attaches twoadjacent conveyor carts 20 and prevents them from becoming completelyseparated should the hitch mechanism 32 fail; second, it enableselectrical continuity among all of the conveyor carts 20 in the train.

The configuration of the conveyor cart 20 of the present invention, withits forwardly mounted roller structure 26, particularly structured hitchmechanism 32, and swept-back fin 36 is a significant improvement overpreviously designed conveyor carts. In conventional conveyor carts, theroller structures are typically mounted at the rear end of the trailerframe and the rear hitch is disposed overtop of the forward hitch. Whena hitch mechanism breaks or becomes accidentally uncoupled with this oldconfiguration, the result is that the forward end of the trailer framedrops below the conveyor track and is pushed over underlying structuresor the floor, leading to inevitable damage to the sorter conveyor.

With the present design, even without the auxiliary connector cable 34,only the rear end of the trailer frame structure 22 will drop below theconveyor track 12 upon accidental disengagement of the hitches 32a,b orupon breakage of the hitch mechanism 32. Therefore, instead of the frontend 36a of the driven fin 36 digging into the floor or underlyingstructures below the conveyor, as is the case with prior art conveyors,the driven fin 36 will simply be dragged with relatively minimal damageshould one of the hitches 32 break or become accidentally uncoupled. Ifan auxiliary connector cable 34 is attached between two adjacent carts20 that break apart, the connector cable 34 will limit the distance thatthe rear end of the trailer frame structure 22 will drop, furtherlimiting damage.

Mounted atop the trailer frame structure 22 of each conveyor cart 20 isthe tiltable support apparatus 50, which supports the carrying tray 40thereabove. As can best be seen in FIG. 5, the tiltable supportapparatus 50 generally includes three components: an upper supportstructure 52 joined to a bottom surface of the carrying tray 40, a lowersupport structure 58 centrally mounted atop the longitudinal base member24, and an angled pivot structure 60 pivotally connecting the lowersupport structure 58 to the upper support structure 52 along a pivotaxis 62.

In turn, the upper support structure 52 includes a front support member54 and a back support member 56. The lower support structure 58 ispreferably generally planar, lying in the vertical plane parallel to theconveyor line of travel 64, and includes an angled upper edge 58a. Thepivot structure 60 preferably includes an axle 68 that runs eitherthrough or along the upper edge 58a of the lower support structure 58and is connected to the front and back support members, 56, 58,respectively. Preferably, the axle 68 runs through lower regions of thefront and back support members 56, 58. As can be seen, the front supportmember 54 depends farther down from the carrying tray 40 than the backsupport member 56. While the lower support structure 58 is stationarilyfixed to the trailer frame 22, the axle 68 allows the upper supportstructure 52 to pivot along the pivot axis 62 of the pivot structure 60.

In an alternate embodiment of the tiltable support apparatus (notshown), the upper support structure 52 could also comprise, like thelower support structure 58, a generally planar member that lies in thevertical plane parallel to the conveyor line of travel 64. In this case,the angled pivot structure 60 could take on the form of a hingestructure joining together the two generally planar support structures52, 58.

The pivot axis 62 lies in a vertical plane parallel to the conveyor lineof travel, which is shown in the drawings as horizontal line 64.However, unlike conventional sorter conveyor tilting carts, the pivotaxis 62 of the conveyor cart 20 of the invention is disposed at an angleθ to the conveyor line of travel 64 so as to impart two axial componentsto the tilting of the carrying tray 40. Preferably, the pivot axis 62 isangled downwardly at an angle of approximately 20 to 45 degrees belowhorizontal in a forward direction. In the embodiment disclosed, thepivot axis 62 is angled downwardly 30 degrees. As can be seen in FIG. 5,the pivot axis 62 preferably intersects a plane occupied by the carryingtray 40 rearward of the center of the tray 40.

By disposing the pivot axis 62 at a downwardly directed angle θ insteadof parallel to the conveyor line of travel 64, two axial components areimparted to the tilting motion of the carrying tray 40. The first axialcomponent of the tray's tilting motion is lateral tipping on ahorizontal axis parallel to the conveyor line of travel 64. The secondaxial component of the tray's tilting motion is rotating around avertical axis 66 perpendicular to the conveyor line of travel. Thus,while the tray only tilts along a single, angled pivot axis 62, theoverall motion of the tray 40 as it tilts includes two axial components.

The tilting motion of the tray may also be described usingthree-dimensional X, Y, and Z-axis spatial coordinates, as shown in FIG.5A, wherein the Y-axis is parallel to the conveyor line of travel 64,the X-axis extends horizontally perpendicular to the line of travel 64,and the Z-axis extends vertically perpendicular to the line of travel64. In the present invention, tilting of the tray 40 includes a Y-axisand a Z-axis component, for as shown in FIG. 5A the pivot axis 62intersects the Y and Z axes. Specifically and for illustrative purposesonly, using the preferred 37.5 degree downward angle θ of the pivot axis62, it can be appreciated that the ratio of Y-axis motion to Z-axismotion is 60:30. In other words, with a 30 degree angle θ, the tray 40laterally tips somewhat farther than it rotates. If the angle θ of thepivot axis 62 is increased to 45 degrees below horizontal, then the traywill tilt and rotate equally.

As shown in FIGS. 6 and 6A, one effect of this two-axis tilting of thecarrying tray 40 is that a side 44b of the tray that is tilteddownwardly also rotates rearwardly relative to the cart 20, as shown inFIG. 6A by line 46a. Side 44d of the tray, which is tilted upwardly,rotates forwardly relative to the cart 20, as shown in FIG. 6A by line46b. In the preferred embodiment, in which the pivot axis 62 intersectsthe plane occupied by the tray 40 rear-of-center, the front side 44a ofthe tray 40 rotates a greater distance around the vertical axis 66 thanthe back side 44c of the tray 40, upon tilting of the tray 40. As shownin FIG. 6A, the bisecting center line of the tray 40 rotates farther atits forward end from the horizontal line of travel 64 than at itsrearward end. Thus, front side rotation line 48a follows a longer arcthan back side rotation line 48b. By rearwardly rotating whichever sideof the tray 40 is being tilted downwardly, some rearward velocity isimparted to packages 11 as they are being discharged from the cart 20 ofthe invention into an unloading station 18. Thus, packages aredischarged at a lower velocity relative to the unloading station thanthe velocity of the train of conveyor carts as a whole. This enables thepackages to be discharged into a narrower chute than could beaccomplished using a conventional conveyor cart. Additionally, becausethe packages are slowed down somewhat as they are discharged, there isless potential for damage to occur.

As can be seen in the drawings, the tray 40 may also include upwardlyangled lateral wings 42 to help prevent packages 11 from accidentallyfalling off the tray 40. These wings 42 also decrease the angle of theslope created when the tray 40 is tilted, which helps with gentlehandling of the packages 11 as they are discharged from the cart 20.

When a carrying tray 40 reaches a particular destination unloadingstation 18, the tilting mechanism 80 tilts the carrying tray 40 to causea package 11 carried thereon to be discharged into the unloading station18. The tilting mechanism 80 generally includes components mounted oneach conveyor cart 20 and components associated with each unloadingstation 18. First is a pair of actuating arms 82 attached beneath eachcart's carrying tray 40 on opposite lateral sides thereof, one actuatingarm 82 on each side of the cart's tiltable support apparatus 50. Secondis a pull-down mechanism 90 immediately upstream from each unloadingstation 18. The pull-down mechanism 90, when activated, selectivelypulls down one of the actuating arms 82 and thereby pulls the respectiveside of the tray 40 downwardly and rearwardly into the biaxially tiltedposition described above. Third is a push-up mechanism 110 downstream ofthe unloading station 18, which pushes up the actuating arm 82 pulleddown by the pull-down mechanism 90 and thereby reorients the tray 40into its normal, upright position. Fourth is a locking structure 120,which locks the carrying tray 40 in the tilted position upon pullingdown of one of the actuating arms 82, and which also locks the carryingtray 40 in its normal, upright position upon pushing up of thatactuating arm 82.

Referring now to FIGS. 7 and 7A, each actuating arm 82 is pivotallyattached to the underside of one side of the carrying tray and ispreferably connected to the front and back support members, 54 and 56respectively, of the upper support structure 52. In the embodimentshown, the actuating arm 82 is attached to the front and back supportmembers by an angled pivot hinge axle 84 that runs through both supportmembers 54, 56 and through the upper end of the actuating arm 82. Theactuating arm 82 therefore pivots on a pivot axis 86 that is preferablyparallel to the pivot axis 62 of the tiltable support apparatus 50, asshown in FIG. 5. As can be seen from an examination of the drawings, theactuating arms 82 and their respective pivot axes 86 remainsubstantially in a vertical plane parallel to the conveyor line oftravel 64 when stationary and when being pulled down or pushed up.

Each actuating arm 82 also includes a roller wheel 88, which engages thepull-down and push-up mechanisms 90, 110, as will be described below.The roller wheel 88 is preferably mounted on the lower end of theactuating arm 82 on an outer surface 82a thereof. It is conceivable,however, that the roller wheel 88 could be replaced with a frictionreducing slide block or other protrusion for engagement by the pull-downand push-up mechanisms 90, 110.

As can be seen from FIGS. 11 and 11A, the actuating arm 82 also includesa bumper assembly 150. The bumper assembly includes an L-shaped bracket152 which extends inwardly from the actuating arm 82 toward the insideof the roller wheel 88 and forwardly in the direction of travel 64. Avertically-oriented bumper 154 is attached to, and extends downwardlyfrom, the L-shaped bracket 152. The bumper 154 is in the same verticalplane as the inside of the roller wheel 88. The bumper 154 may consistof a rod fixably attached to a hole 156 in the end 152a of the L-shapedbracket 152. A sleeve 158 may be rotatably attached to the lower end154a of the bumper 154.

Seen in detail in FIGS. 8, 8A, 9, and 9A, a pull-down mechanism 90 isassociated with each unloading station 18 and is located beneath therail 14 running closest to the unloading station 18 on the upstream sidethereof, as indicated in FIG. 6A. The pull-down mechanism 90 includes adescending ramp 92 and a laterally pivoting switch 94 that, whenactuated, pivots open and directs the roller wheel 88 of a passingactuating arm 82 into the descending ramp 92. As can be seen in thedrawings, when the switch 94 is not actuated, the switch is in a closedposition parallel to the ramp 92, and the roller wheel 88 is free tobypass the switch and the descending ramp 92. However, when a particularpackage 11 arrives at its destination unloading station 18, the switch94 is automatically actuated so that it pivots open into the path of thepassing roller wheel 88, capturing the roller wheel 88. The roller wheel88 then rolls through the switch 94, causing the actuating arm 82 topivot outwardly somewhat, and into the descending ramp 92.

As the roller wheel 88 rolls through the switch 94, the bumper 154 orsleeve 158 engages a closure flange 104 having a curved end 106 tothereby pivot the switch 94 back to its closed position, as the rollerwheel 88 exits the switch 94 and enters the descending ramp 92.

In an alternative embodiment, as the sleeve 158 engages the closureflange 104, the sleeve 158 rotates around the bumper 154 to reduce thefriction created by the sleeve 158 contacting the closing flange 104.Next, the descending ramp 92 forces the roller wheel 88 and theassociated actuating arm 82 downwardly so as to pull down one side ofthe tray 40, thereby discharging the package from the tray 40 into theunloading station 18 adjacent the pull-down mechanism 90.

A computer controller (not shown) is used to track all packages 11moving on the conveyor 10 and to automatically actuate a switch 94 atthe appropriate time when a particular package 11 reaches itsdestination unloading station or outfeed chute 18. The computer is alsoconnected to the LIM 70 to control the movement of the conveyor trainand maintain a desirable rate of speed.

In a preferred embodiment of the switch 94, a biasing member 96, such asa coil spring, is used to constantly urge the laterally pivoting switch94 towards its open position. However, to prevent the switch 94 fromalways remaining open and thereby capturing every passing roller wheel88, a lock catch 98 is provided to hold the switch closed. The lockcatch 98 pivots on a horizontal pivot member 98a between the normal,horizontal position shown in FIG. 8A, which holds the switch 94 closed,and the tilted position shown in FIG. 8, which allows the switch 94 toswing open.

A catch 102 depending from the forward end of the switch 94 engages anoutboard side of the lock catch 98 as the switch is held closed. Whenthe switch 94 is closed by the action of the passing bumper 152 on theclosure flange 104, the depending catch 102 slides over a slanted end98b of the lock catch 98 back into position on the outboard side of thelock catch 98.

Beneath the forward end 98c of the lock catch 98 opposite the slantedend 98b is a vertically oriented solenoid 100, which is actuated by thecomputer controller. Upon receiving a short pulse of electricity fromthe computer controller, the vertical solenoid 100 pushes the forwardend 98c of the lock catch 98 upwardly to pivot the lock catch 98 andrelease the depending catch 102 of the switch 94. The switch 94 is thenswung into its open position by the biasing spring 96, where it capturesthe next passing roller wheel 88.

After the carrying tray 40 has been tilted and a package carried thereonhas been discharged into an unloading station 18, the carrying tray isreoriented into its normal upright position by the push-up mechanism110. Seen best in FIGS. 10 and 10A, a push-up mechanism 110 isassociated with each unloading station 18 and is located beneath thetrack 12 adjacent the unloading station 18 on the downstream sidethereof, as indicated in FIG. 6A. Each push-up mechanism 110 includes anascending ramp 112 below the rail 14 adjacent the unloading station 18.The push-up mechanism 110 also includes a wedge-shaped frog 114 thatengages the roller wheel 88 on a pulled-down actuating arm 82 anddirects the roller wheel 88 into the ascending ramp 112. The frog 114 ispositioned low enough below the track 12 so that roller wheels 88 willbe engaged and directed into the ascending ramp 112 only if they havealready been pulled down by the pull-down mechanism 90. As the rollerwheel 88 is directed into the ascending ramp 112, the actuating arm 82is pivoted outwardly somewhat so that the outside edge 123 of thelocking flange 122 will disengage from the tilted position lockingchannel 127. To help pull the actuating arm 82 back into substantiallyvertical alignment after the locking flange 122 has slid over the slidesurface 130, the top of the ascending ramp 112 includes an inwardlyturned section 116.

Now turning to the locking structure 120 of the tilting mechanism 80, itcan be seen best in FIGS. 7 and 7A that the locking structure 120includes a pair of locking flanges 122, a pair of locking blocks 124mounted one each to the actuating arms 82, and a biasing member 134 forbiasing the actuating arms 82 inwardly into a locked position.Preferably, the locking flanges 122 laterally extend from both sides ofthe lower support structure 58 of the tiltable support apparatus 50,although they could also be mounted to the trailer frame structure 22.In the embodiment disclosed, the locking flanges 122 comprise generallyplanar steel plates having rollers 123 mounted to their outer edges 123.In an alternate embodiment, the rollers 123 could be eliminated and thelocking blocks 124 made of a low-friction material on which theroller-less outer edges of the locking flanges 122 could easily slide.

Each locking block 124 is mounted to an inner surface 82a of theactuating arm 82 and includes two locking channels 126 and 134 separatedby a cammed section 130 having a generally convex outer surface. Thelower 126 of the two locking channels receives the roller 123 at theouter edge of the lateral locking flange 122 when the carrying tray 40is in its upright position. The upper 134 of the two locking channelsreceives the roller 123 when the carrying tray 40 is in its tiltedposition. As the tray 40 is tilted from one position to the other, theroller 123 rolls over the cammed section 130 interposed between the twolocking channels 126, 134. Preferably, the locking blocks 124 are madeof a wear resistant material such as plastic, although other materialscould be used. The biasing member, which may be a spring 134, pulls theactuating arms 82 inwardly so as to engage the locking structure 120 byseating the locking flanges 122 in one of the locking channels 126, 134.

During tilting of the tray 40 by the pull-down mechanism 90, theactuating arm 82 being pulled down is pivoted outward slightly on thepivot axis 86 as the roller wheel 88 is captured by the switch 94 anddirected into the descending ramp 92. This outward pivoting of theactuating arm 82 causes the upright position locking channel 126 todisengage from the locking flange 122. Then, as the roller wheel 88 ispulled down by the descending ramp 92, the locking flange 122 rollsupwardly over the cammed section 130. Because of the curved, convexshape of the cammed section 130 of the locking block 124, the actuatingarm 82 remains substantially vertical as it is pulled down. This helpsprevent the roller wheel 88 from slipping out of the descending ramp 92of the pull-down mechanism 90. Eventually, the locking flange 122 isseated in the tilted position locking channel 134 as the wheel exits thedescending ramp 92 and the tray 40 reaches its fully tilted position.The degree to which the tray 40 is tilted in the fully tilted positioncan vary depending on the configuration of the locking blocks 124 andthe pull-down mechanism 90. However, in the embodiment disclosed, thetray 40 is tilted approximately 37.5 degrees from horizontal in thefully tilted position.

The biasing member 134 holds the tilted position locking channel 134 andthe locking flange 122 together while the cart 20 is moving past theunloading station 18, stabilizing the tray 40 in the tilted position.Then, when the downwardly pulled actuating arm 82 reaches the push-upmechanism, the arm 82 is pivoted outwardly by the wedge-shaped frog 114engaging the roller wheel 88. This outward pivoting causes the lockingflange 122 to disengage from the tilted position locking channel 134. Asthe roller wheel 88 moves up the ascending ramp 112, the locking flangerolls downwardly over the cammed section 130. As the inwardly turned topend 116 of the ascending ramp 112 pivots the actuating arm 82 back toits vertical orientation, the locking flange 122 seats in the uprightposition locking channel 126, where it is held in place through theaction of the biasing member 134.

The actuating arm 82 on the opposite side of the conveyor cart 20, whichis not being pulled down or pushed up at a particular unloading station18, simply rises and falls with the side of the tray 40 to which it isattached. The locking flange 122 on this side of the cart 20 simplyrolls over a flat section 132 of the locking block 124 below the uprightposition locking channel 126.

In an alternate embodiment (not shown) of the package sorting conveyor10 of the invention, the conveyor cart 20 could include a tiltablesupport apparatus having a pivot axis that is not angled downwardly butthat is generally parallel to the conveyor line of travel 64. In thiscase, the tilting motion of the carrying tray 40 would only have asingle axial component--lateral tipping on a horizontal axis parallel tothe conveyor line of travel 64. While package sorting conveyors having asingle-axis lateral tipping motion have been designed in the past, theydo not include the other inventive features of the present sortingconveyor 10 such as the vertically oriented LIM 70, the hitch mechanism32 and auxiliary cart connector 34, and the tilting mechanism 80 withits associated components.

Such single-axis conveyor carts would primarily be incorporated into thepackage sorting conveyor 10 of the present invention for use in sortingparticularly large packages that must be carried by two or more adjacentcarrying carts 20. In this case, the trays of the adjacent carts wouldbe simultaneously tilted as the carts reached an unloading station todischarge the package. This would also of course require an especiallywide outfeed chute as well as a pull-down mechanism adjacent theunloading station for each cart to be simultaneously tilted.

The reason that single-axis conveyor carts are especially useful forsorting large packages is that it has been found that this double (ortriple, etc.) unloading of particularly large packages using thetwo-axis carrying carts 20 of the present invention occasionallypresents difficulties due to the carrying trays 40 not being in the samespatial plane when they are both in their fully tilted positions.Therefore, for double unloading, it is preferable to use the alternate,single-axis embodiment of the conveyor cart.

Several configurations of the package sorting conveyor 10 may beemployed that utilize the alternate, single-axis conveyor carts fordouble unloading situations. A preferable configuration would comprisetwo adjacent single-axis carts for carrying a single large package. Asecond configuration would comprise a leading two-axis conveyor cart 20and a trailing single-axis cart. A third configuration would comprise aleading single-axis conveyor cart and a trailing two-axis conveyor cart20. As a whole, the package sorting conveyor 10 of the invention mayinclude both two-axis conveyor carts 20 as well as single-axis conveyorcarts interspersed among each other depending on a particular facility'sconveying and sorting requirements.

Certain modifications and improvements will occur to those skilled inthe art upon a reading of the foregoing description. It should beunderstood that all such modifications and improvements have beendeleted herein for the sake of conciseness and readability but areproperly within the scope of the following claims.

I claim:
 1. A sorting conveyor for transporting objects and unloadingobjects at one or more unloading stations adjacent the conveyor, saidsorting conveyor comprising:(a) a conveyor track; (b) a train of tiltingconveyor carts connected end-to-end; (c) a power source for moving saidconveyor carts on said conveyor track; (d) each of said tilting conveyorcarts comprising: (i) a trailer frame base, including: a rollerstructure for engaging said conveyor track, a driven member responsiveto said power source, and a hitch mechanism for connecting each tiltingconveyor cart to an adjacent conveyor cart; (ii) a carrying tray forholding the objects; and (iii) a tiltable support apparatus forsupporting said carrying tray above said trailer frame base and forallowing tilting of said carrying tray towards at least one side of theconveyor to unload objects into unloading stations on at least one sideof the conveyor, said tiltable support apparatus including: (i) an uppersupport structure joined to said carrying tray, (ii) a lower supportstructure joined to said trailer frame base, and (iii) a pivot structureconnecting the upper support structure to the lower support structurealong a pivot axis; and (e) a tilting mechanism for tilting saidcarrying tray on said tiltable support apparatus to thereby unloadobjects into one of the unloading stations adjacent the conveyor,wherein said tilting mechanism includes: (i) a pair of actuating armsattached to said carrying tray on opposite sides of said tiltablesupport apparatus; and (ii) a pull-down mechanism associated with eachunloading station for selectively pulling down one of said actuatingarms so as to pull one side of said carrying tray downwardly andrearwardly into a tilted position; wherein each of said actuator armsincludes a roller wheel on a lower end of said actuator arm and a bumperlocated in front of the leading inside edge of said roller wheel, andwherein said pull-down mechanism includes a descending ramp adjacentsaid conveyor track and a laterally pivoting switch for engaging saidbumper and directing the roller wheel of a selected actuator arm intosaid descending ramp.
 2. The apparatus according to claim 1, whereinsaid tilting mechanism further comprises a locking structure for lockingsaid carrying tray in the tilted position upon pulling down of one ofsaid actuating arms, and for locking said carrying tray in the uprightposition upon pushing up of said actuating arm.
 3. The apparatusaccording to claim 1, wherein said actuating arms are each pivotallyattached to said carrying tray beneath said carrying tray.
 4. Theapparatus according to claim 3, wherein the pivot axes of said actuatingarms are parallel to the pivot axis of said tiltable support apparatus.5. The apparatus according to claim 3, wherein said actuating arms arepivotally attached to said upper support structure of said tiltablesupport apparatus.
 6. The apparatus according to claim 3, wherein thepivot axis of said pivot structure lies in a vertical plane parallel tothe conveyor line of travel, and wherein said actuating arms remainsubstantially parallel to the vertical plane parallel to the conveyorline of travel during pulling down and pushing up of said actuating armsto tilt said carrier tray.
 7. The apparatus according to claim 1,further including means for opening said laterally pivoting switch so asto capture a selected roller wheel and direct the roller wheel into thedescending ramp, and means for closing said laterally pivoting switchafter capture of the roller wheel.
 8. The apparatus according to claim7, wherein the means for opening said laterally pivoting switchincludes:(a) a biasing member for urging said switch into an openposition; (b) a lock catch to prevent opening of said switch until aselected time; and (c) a solenoid for actuating the lock catch so as topermit the biasing member to open said switch.
 9. The apparatusaccording to claim 8, wherein said solenoid is vertically mountedbeneath the lock catch.
 10. The apparatus according to claim 7, whereinthe means for closing said laterally pivoting switch includes a closureflange mounted on said switch and responsive to passing of said rollerwheel.
 11. The apparatus according to claim 2, wherein said lockingstructure includes:(a) a pair of laterally extending locking flanges onopposite sides of said tiltable support apparatus; (b) a pair of lockingblocks mounted to inner surfaces of said actuating arms, each lockingblock having locking channels that receive said locking flanges; and (c)a biasing member attached to both actuating arms for biasing saidactuating arms towards each other so as to urge said each of saidlocking flanges into one of said locking channels.
 12. The apparatusaccording to claim 11, wherein each locking block includes a lockingchannel associated with the tilted position of said carrying tray, andwherein each locking block includes a locking channel associated withthe upright position of said carrying tray.
 13. The apparatus accordingto claim 12, wherein each said locking flange includes a roller mountedto an outer edge thereof.
 14. The apparatus according to claim 13,wherein each said locking block includes a cammed section between saidlocking channels over which said rollers on the outer edges of saidlocking flanges roll.
 15. The apparatus according to claim 1, whereinsaid conveyor track comprises two parallel rails.
 16. The apparatusaccording to claim 15, wherein said trailer frame base includes alongitudinal base member that extends between the two parallel railsparallel to the conveyor line of travel.
 17. The apparatus according toclaim 16, wherein said roller structure comprises two laterallyextending roller wheel mechanisms, one roller wheel mechanism riding oneach conveyor track rail.
 18. The apparatus according to claim 15,wherein each said roller wheel mechanism includes an axle caster thatholds a roller wheel, each said axle caster including two forks, abearing bore disposed at a juncture between said two forks, and at leastone flange bearing seated within said bearing bore and disposed aroundan axle shaft extending from said roller structure.
 19. The apparatusaccording to claim 18, wherein said roller wheel is held in place insaid axle caster by a nut and bolt extending through said roller wheeland both of said forks, wherein said axle caster also includes anopening on one side of said bearing bore that communicates with a spacebetween said two forks, and wherein said at least one flange bearing issecured within said bearing bore by tightening said nut and bolt so asto inwardly flex said two forks towards each other, thereby slightlyclosing said opening and distorting said bearing bore.
 20. The apparatusaccording to claim 17, wherein each conveyor track rail is supportedonly on an outside edge, and wherein each roller wheel mechanismcomprises three roller wheels.
 21. The apparatus according to claim 20,wherein each roller wheel mechanism includes an upper roller wheel forriding on a top edge of a track rail, a middle roller wheel for ridingon an inside edge of the track rail, and a lower wheel for riding on abottom edge of the track rail.
 22. The apparatus according to claim 17,wherein the roller wheel mechanisms are attached to a forward end ofsaid longitudinal base member.
 23. The apparatus according to claim 1,wherein said power source comprises a linear induction motor, andwherein the driven member of said trailer frame base comprises a metalfin moved in the conveyor line of travel by said linear induction motor.24. The apparatus according to claim 23, wherein said linear inductionmotor and said metal fin are both vertically oriented beneath saidtrailer frame base.
 25. The apparatus according to claim 24, whereinsaid metal fin is generally parallelogram-shaped with rearwardly angledfront and rear edges.
 26. The apparatus according to claim 23, whereinsaid linear induction motor comprises two opposing out-of-phaseelectromagnets.
 27. The apparatus according to claim 1, wherein saidhitch mechanism comprises a front hitch on a front end of said trailerframe base, a rear hitch on a rear end of said trailer frame base, and ahitch connector for connecting the front hitch of one conveyor cart tothe rear hitch of an adjacent conveyor cart.
 28. The apparatus accordingto claim 27, wherein the front hitch is disposed overtop of the rearhitch.
 29. The apparatus according to claim 1, wherein said trailerframe base comprises an auxiliary cart connector for connecting eachtilting conveyor cart to an adjacent conveyor cart to prevent adjacentconveyor carts from separating upon failure of said hitch mechanism. 30.The apparatus according to claim 29, wherein said auxiliary cartconnector comprises an electrically conductive cable connected at oneend to said trailer frame base and at another end to a trailer framebase of an adjacent conveyor cart.
 31. The apparatus according to claim1, wherein said sorting conveyor includes at least one single-axisconveyor cart that comprises a tiltable support apparatus having ahorizontal pivot axis that is disposed generally parallel to theconveyor line of travel.
 32. A sorting conveyor for transporting objectsand unloading objects at one or more unloading stations adjacent theconveyor, said sorting conveyor comprising:(a) a conveyor track; (b) atrain of tilting conveyor carts connected end-to-end; (c) a power sourcefor moving said conveyor carts on said conveyor track, wherein saidpower source comprises a linear induction motor; (d) each of saidtilting conveyor carts comprising: (i) a trailer frame base, including:a roller structure for engaging said conveyor track, a driven memberresponsive to said power source, and a hitch mechanism for connectingeach tilting conveyor cart to an adjacent conveyor cart; (ii) a carryingtray for holding the objects; and (iii) a tiltable support apparatus forsupporting said carrying tray above said trailer frame base and forallowing tilting of said carrying tray towards at least one side of theconveyor to unload objects into unloading stations on at least one sideof the conveyor, said tiltable support apparatus including: (i) an uppersupport structure joined to said carrying tray, (ii) a lower supportstructure joined to said trailer frame base, and (iii) a pivot structureconnecting the upper support structure to the lower support structurealong a pivot axis; and (e) a tilting mechanism for tilting saidcarrying tray on said tiltable support apparatus to thereby unloadobjects into one of the unloading stations adjacent the conveyor,wherein said tilting mechanism includes: (i) a pair of actuating armsattached to said carrying tray on opposite sides of said tiltablesupport apparatus; and (ii) a pull-down mechanism associated with eachunloading station for selectively pulling down one of said actuatingarms so as to pull one side of said carrying tray downwardly andrearwardly into a tilted position; wherein each of said actuator armsincludes a roller wheel on a lower end of said actuator arm and a bumperassembly located in front of the leading inside edge of said rollerwheel, said bumper assembly including: (i) a downwardly extending,vertically oriented bumper; and (ii) means for positioning saiddownwardly extending, vertically oriented bumper with respect to theinside leading edge of said roller wheel, and wherein said pull-downmechanism includes a descending ramp adjacent said conveyor track and alaterally pivoting switch for engaging said bumper and directing theroller wheel of a selected actuator arm into said descending ramp. 33.The apparatus according to claim 32, wherein said tilting mechanismfurther comprises a locking structure for locking said carrying tray inthe tilted position upon pulling down of one of said actuating arms, andfor locking said carrying tray in the upright position upon pushing upof said actuating arm.
 34. The apparatus according to claim 32, whereinsaid actuating arms are each pivotally attached to said carrying traybeneath said carrying tray.
 35. The apparatus according to claim 34,wherein the pivot axes of said actuating arms are parallel to the pivotaxis of said tiltable support apparatus.
 36. The apparatus according toclaim 34, wherein said actuating arms are pivotally attached to saidupper support structure of said tiltable support apparatus.
 37. Theapparatus according to claim 34, wherein the pivot axis of said pivotstructure lies in a vertical plane parallel to the conveyor line oftravel, and wherein said actuating arms remain substantially parallel tothe vertical plane parallel to the conveyor line of travel duringpulling down and pushing up of said actuating arms to tilt said carriertray.
 38. The apparatus according to claim 32, further including meansfor opening said laterally pivoting switch so as to capture a selectedroller wheel and direct the roller wheel into the descending ramp, andmeans for closing said laterally pivoting switch after capture of theroller wheel.
 39. The apparatus according to claim 38, wherein the meansfor opening said laterally pivoting switch includes:(a) a biasing memberfor urging said switch into an open position; (b) a lock catch toprevent opening of said switch until a selected time; and (c) a solenoidfor actuating the lock catch so as to permit the biasing member to opensaid switch.
 40. The apparatus according to claim 39, wherein saidsolenoid is vertically mounted beneath the lock catch.
 41. The apparatusaccording to claim 38, wherein the means for closing said laterallypivoting switch includes a closure flange mounted on said switch andresponsive to passing of said roller wheel.
 42. The apparatus accordingto claim 23, wherein said locking structure includes:(a) a pair oflaterally extending locking flanges on opposite sides of said tiltablesupport apparatus; (b) a pair of locking blocks mounted to innersurfaces of said actuating arms, each locking block having lockingchannels that receive said locking flanges; and (c) a biasing memberattached to both actuating arms for biasing said actuating arms towardseach other so as to urge said each of said locking flanges into one ofsaid locking channels.
 43. The apparatus according to claim 42, whereineach locking block includes a locking channel associated with the tiltedposition of said carrying tray, and wherein each locking block includesa locking channel associated with the upright position of said carryingtray.
 44. The apparatus according to claim 43, wherein each said lockingflange includes a roller mounted to an outer edge thereof.
 45. Theapparatus according to claim 44, wherein each said locking blockincludes a cammed section between said locking channels over which saidrollers on the outer edges of said locking flanges roll.
 46. Theapparatus according to claim 32, wherein said conveyor track comprisestwo parallel rails.
 47. The apparatus according to claim 46, whereinsaid trailer frame base includes a longitudinal base member that extendsbetween the two parallel rails parallel to the conveyor line of travel.48. The apparatus according to claim 44, wherein said roller structurecomprises two laterally extending roller wheel mechanisms, one rollerwheel mechanism riding on each conveyor track rail.
 49. The apparatusaccording to claim 46, wherein each said roller wheel mechanism includesan axle caster that holds a roller wheel, each said axle casterincluding two forks, a bearing bore disposed at a juncture between saidtwo forks, and at least one flange bearing seated within said bearingbore and disposed around an axle shaft extending from said rollerstructure.
 50. The apparatus according to claim 49, wherein said rollerwheel is held in place in said axle caster by a nut and bolt extendingthrough said roller wheel and both of said forks, wherein said axlecaster also includes an opening on one side of said bearing bore thatcommunicates with a space between said two forks, and wherein said atleast one flange bearing is secured within said bearing bore bytightening said nut and bolt so as to inwardly flex said two forkstowards each other, thereby slightly closing said opening and distortingsaid bearing bore.
 51. The apparatus according to claim 48, wherein eachconveyor track rail is supported only on an outside edge, and whereineach roller wheel mechanism comprises three roller wheels.
 52. Theapparatus according to claim 51, wherein each roller wheel mechanismincludes an upper roller wheel for riding on a top edge of a track rail,a middle roller wheel for riding on an inside edge of the track rail,and a lower wheel for riding on a bottom edge of the track rail.
 53. Theapparatus according to claim 48, wherein the roller wheel mechanisms areattached to a forward end of said longitudinal base member.
 54. Theapparatus according to claim 32, wherein the driven member of saidtrailer frame base comprises a metal fin moved in the conveyor line oftravel by said linear induction motor.
 55. The apparatus according toclaim 54, wherein said linear induction motor and said metal fin areboth vertically oriented beneath said trailer frame base.
 56. Theapparatus according to claim 55, wherein said metal fin is generallyparallelogram-shaped with rearwardly angled front and rear edges. 57.The apparatus according to claim 54, wherein said linear induction motorcomprises two opposing out-of-phase electromagnets.
 58. The apparatusaccording to claim 32, wherein said hitch mechanism comprises a fronthitch on a front end of said trailer frame base, a rear hitch on a rearend of said trailer frame base, and a hitch connector for connecting thefront hitch of one conveyor cart to the rear hitch of an adjacentconveyor cart.
 59. The apparatus according to claim 58, wherein thefront hitch is disposed overtop of the rear hitch.
 60. The apparatusaccording to claim 32, wherein said trailer frame base comprises anauxiliary cart connector for connecting each tilting conveyor cart to anadjacent conveyor cart to prevent adjacent conveyor carts fromseparating upon failure of said hitch mechanism.
 61. The apparatusaccording to claim 60, wherein said auxiliary cart connector comprisesan electrically conductive cable connected at one end to said trailerframe base and at another end to a trailer frame base of an adjacentconveyor cart.
 62. The apparatus according to claim 32, wherein saidsorting conveyor includes at least one single-axis conveyor cart thatcomprises a tiltable support apparatus having a horizontal pivot axisthat is disposed generally parallel to the conveyor line of travel. 63.The apparatus according to claim 32, wherein said downwardly extending,vertically oriented bumper is a wear resistant rod.
 64. The apparatusaccording to claim 63, further including a sleeve rotatably attached tothe lower end of said rod.
 65. The apparatus according to claim 32,wherein said means for positioning said bumper with respect to theinside leading edge of said roller wheel is a bracket attached to theactuating arm.
 66. The apparatus according to claim 65, wherein saidbracket is L-shaped.
 67. The apparatus according to claim 65, whereinsaid bracket is integrally molded into the actuating arm.